Grids and methods and apparatus for forming same



United States Patent O GRIDS AND NIETHODS AND APPARATUS FOR FORMING SAME James R. Eisan, Natick, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation This invention relates to flat-formed grids and the method and apparatus for forming such grids, and more particularly to grids with the planes of the strands lying between planes tangent to the supporting rods.

In certain electronic tube structures, it is desirable to have a grid formed on supporting rods with the cross strands of the grid wire lying in planes parallel to and between planes tangent to the supporting rods. With such a grid, it is diicult to control the spacing between the layers of strands and to prevent the supporting rods from being drawn together in the process of forming the grid. It is also difficult to assurethat, once the grid wires are pressed into shape, they will retain that shape. By the methods of this invention, the grid wire is wound about and attached to the supporting rods, and a mandril is inserted within the grid. The mandril has a width equal to the desired spacing of the supporting rods, and a thickness equal to the desired spacing between the layer of strands and recesses near the rods to receive loops of excess grid wire. The grid, with the mandril inside, is placed Within a two-part die that is shaped so that, when the two parts of the die are pressed together, the layers of strands of grid wire are forced towards each other and against the mandril. At the same time, any excess lengths of strands of grid Wire are pushed into loops near the supporting rods by protrusions or ridges on the interior of the two parts of the die. This action causes the strands of grid wire to take a permanent set in the desired shape, and to retain this shape after the grid is removed from the dies and the mandril is removed from within the grid.

Other and further advantages and objects of this invention will be apparent as the description thereof progresses, reference being had to the accompanying drawings wherein:

Fig. l is a side elevation of a grid constructed according to the invention;

Fig. 2 is an enlarged section taken along the line 2-2 of Fig. 1 of the grid after winding and before forming; and

Fig. 3 is a section similar to that of Fig. 2 of the grid, the die, and the mandril during forming.

In Fig. l, the reference numerals and 11 designate the supporting rods about which a grid wire 12 is wound and supported in notches 13, the edges of which are swedged over the grid wire to ix each strand in place.

From Fig. 2 it will be seen that the strands of grid wire Patented June 4, 1957 'ice 12 bow out away from the plane of the axes of the supporting rods.

In order to arrange the strands of the grid wire 12 in two parallel planes, parallel to the plane of the axes of the supporting rods and between planes tangent to these rods 10 and 11, a mandril 14 is positioned within the wound grid. This mandril is formed with a width equal to the desired spacing of the supporting rods 10 and 11, and of a thickness equal to the desired spacing between the layers of strands of the grid wire 12, and is formed with recesses 15, 16, 17, and 18 near where it makes contact with the support rods when inserted within the wound grid. The grid, with the mandril 14 inserted within it, is positioned within the two parts 20 and 21 of a die formed to receive the grid and mandril, and having ridges 22, 23, 24, and 25 formed to cooperate with the recesses 15, 16, 17, and 18 in the mandril 14 to shape the grid strands into loops 26, 27, 28, and 30 to absorb any excess grid wire and stiften the structure against lateral movement in the plane of support rods 10 and 11. After pressure is applied to the grid through the two parts 20 and 21 of the die, the grid wire 12 is work-hardened and stiifened to produce a structure that, in a representative case, was found to be forty percent more rigid than a grid that is merely wound.

'Ihis invention is not limited to the particular details of construction, materials and processes described, as many equivalents will suggest themselves to those skilled in the art. It is, accordingly, desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. A grid structure for an electron discharge device comprising a pair of parallel supporting rods in a common plane, and a conductor wound about the supporting rods with strands extending throughout their useful length between the rods in two substantially parallel planes parallel to and between planes tangent to the supporting rods, each strand formed with an indented region near each supporting rod projecting within the planes of the strands.

2.. Apparatus for forming a grid with strands of wire between two supporting rods disposed in two parallel planes parallel to two planes tangent to the supporting rods comprising a mandril of rectangular cross section of a width equal to the desired spacing of the supporting rods of a thickness equal to the desired spacing between the planes of the strands and formed with recesses in the longitudinal edges, and dies formed to receive the wound grid and mandril and having protrusions formed in them adapted to force the strands into the recesses in the mandril and press the grid in against the mandril to give it the desired shape.

References Cited in the ile of this patent UNITED STATES PATENTS 2,507,709 Gronros May 16, 1950 FOREIGN PATENTS 321,553 Great Britain Nov. 14, 1929 428,478 Great Britain May 14. 1935 

